A common technique of making spring mattresses is the so-called pocket technique. This means that the springs are enclosed in pockets, that is they are individually surrounded by a casing material. In this way, the springs will be relatively individually resilient so that they can flex individually without affecting the neighbouring springs and, thus, the comfort of the user increases since his weight will be distributed more uniformly over the surface that receives the load.
A drawback of this type of mattresses is, however, that they are often relatively soft, which makes it difficult to move in the bed as the user is to turn or sit up in the bed for instance. Moreover, there is a risk of falling out of the bed when lying close to the edge or when sitting down on the edge, which may cause injuries and discomfort.
For example GB 225 225, U.S. Pat. No. 2,878,012 and U.S. Pat. No. 2,359,003 also disclose cushions to be used as vehicle seats with coil springs, where surrounding casings are airtight and check valves or the like are provided to limit the flow of air into the casings. As a result, damping is provided, which makes the returning of the coil springs to an extended position difficult, which reduces swinging and oscillation when the vehicle drives over an uneven road and the like. These cushions are, however, neither intended nor suitable for use in beds and are besides of another type than conventional pocket mattresses, comprising separate enclosed spring units which are widely scattered in the mattress.
Moreover U.S. Pat. No. 5,467,489 suggests a pocket mattress where coils springs are enclosed in airtight casings and where check valves are arranged in the bottom and exhaust passages at the top. This results in an airflow through the mattress, which gives a cooling effect to the user. However, no damping is achieved. Also this mattress is of another type than conventional pocket mattresses, comprising separate pocket units which are interconnected by flexible links.
There is thus a need for a pocket mattress which can be made soft and comfortable and still allow the user to move relatively easily and where the risk of the user falling out of the bed is reduced. There is also a need for a pocket mattress which, while maintaining the positive properties of pocket mattresses in general, also has certain properties that remind of mattresses of visco-elastic materials, such as an initially slow sinking into the mattress when laying down on it. It is also desirable that a mattress with the above-mentioned properties can be manufactured relatively easily and cost-effectively.